Sforno on Exodus 9:14/ספורנו על שמות ט׳:י״ד

1כי בפעם הזאת, this time when I demonstrate My power over the third category of phenomena, the atmosphere and what it contains, אני שולח את כל מגפותי אל לבך ובעבדיך ובעמך, every plague which I am about to send will affect each one of you even after the plague itself departs. The damage caused by the plague while it was active will be felt long after the plague has departed. The after-effect could be felt because of the vegetables remaining having suffered damage from the hail. The unnatural type of darkness would also leave behind it unpleasant after-effects, as the whole atmosphere would have been affected during the period of no light. If we consider that for three days running no one could even rise from his chair or bed, we can imagine that this was not merely an absence of daylight. The plagues that had preceded the hail had not left behind them permanent after-effects.

2בעבור תדע כי אין כמוני בכל הארץ, this realisation will come to you when you observe how I enjoy complete mastery of the atmosphere. G’d reserved the demonstration that He also had complete control of all the phenomena in outer space, or in extra terrestrial regions for the time when He split the Sea of Reeds. When the Egyptians observed the movements of the pillars of fire and the columns of cloud, all of which moved in a manner which reflected that they were being directed by a higher power.